/*
 * Copyright 2002-2017 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.servlet.support;

import org.springframework.context.MessageSource;
import org.springframework.context.support.MessageSourceResourceBundle;
import org.springframework.context.support.ResourceBundleMessageSource;
import org.springframework.lang.Nullable;

import javax.servlet.ServletContext;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpSession;
import javax.servlet.jsp.jstl.core.Config;
import javax.servlet.jsp.jstl.fmt.LocalizationContext;
import java.util.Locale;
import java.util.ResourceBundle;
import java.util.TimeZone;

/**
 * Helper class for preparing JSTL views,
 * in particular for exposing a JSTL localization context.
 *
 * @author Juergen Hoeller
 * @since 20.08.2003
 */
public abstract class JstlUtils {

    /**
     * Checks JSTL's "javax.servlet.jsp.jstl.fmt.localizationContext"
     * context-param and creates a corresponding child message source,
     * with the provided Spring-defined MessageSource as parent.
     *
     * @param servletContext the ServletContext we're running in
     *                       (to check JSTL-related context-params in {@code web.xml})
     * @param messageSource  the MessageSource to expose, typically
     *                       the ApplicationContext of the current DispatcherServlet
     * @return the MessageSource to expose to JSTL; first checking the
     * JSTL-defined bundle, then the Spring-defined MessageSource
     * @see org.springframework.context.ApplicationContext
     */
    public static MessageSource getJstlAwareMessageSource(
            @Nullable ServletContext servletContext, MessageSource messageSource) {

        if (servletContext != null) {
            String jstlInitParam = servletContext.getInitParameter(Config.FMT_LOCALIZATION_CONTEXT);
            if (jstlInitParam != null) {
                // Create a ResourceBundleMessageSource for the specified resource bundle
                // basename in the JSTL context-param in web.xml, wiring it with the given
                // Spring-defined MessageSource as parent.
                ResourceBundleMessageSource jstlBundleWrapper = new ResourceBundleMessageSource();
                jstlBundleWrapper.setBasename(jstlInitParam);
                jstlBundleWrapper.setParentMessageSource(messageSource);
                return jstlBundleWrapper;
            }
        }
        return messageSource;
    }

    /**
     * Exposes JSTL-specific request attributes specifying locale
     * and resource bundle for JSTL's formatting and message tags,
     * using Spring's locale and MessageSource.
     *
     * @param request       the current HTTP request
     * @param messageSource the MessageSource to expose,
     *                      typically the current ApplicationContext (may be {@code null})
     * @see #exposeLocalizationContext(RequestContext)
     */
    public static void exposeLocalizationContext(HttpServletRequest request, @Nullable MessageSource messageSource) {
        Locale jstlLocale = RequestContextUtils.getLocale(request);
        Config.set(request, Config.FMT_LOCALE, jstlLocale);
        TimeZone timeZone = RequestContextUtils.getTimeZone(request);
        if (timeZone != null) {
            Config.set(request, Config.FMT_TIME_ZONE, timeZone);
        }
        if (messageSource != null) {
            LocalizationContext jstlContext = new SpringLocalizationContext(messageSource, request);
            Config.set(request, Config.FMT_LOCALIZATION_CONTEXT, jstlContext);
        }
    }

    /**
     * Exposes JSTL-specific request attributes specifying locale
     * and resource bundle for JSTL's formatting and message tags,
     * using Spring's locale and MessageSource.
     *
     * @param requestContext the context for the current HTTP request,
     *                       including the ApplicationContext to expose as MessageSource
     */
    public static void exposeLocalizationContext(RequestContext requestContext) {
        Config.set(requestContext.getRequest(), Config.FMT_LOCALE, requestContext.getLocale());
        TimeZone timeZone = requestContext.getTimeZone();
        if (timeZone != null) {
            Config.set(requestContext.getRequest(), Config.FMT_TIME_ZONE, timeZone);
        }
        MessageSource messageSource = getJstlAwareMessageSource(
                requestContext.getServletContext(), requestContext.getMessageSource());
        LocalizationContext jstlContext = new SpringLocalizationContext(messageSource, requestContext.getRequest());
        Config.set(requestContext.getRequest(), Config.FMT_LOCALIZATION_CONTEXT, jstlContext);
    }


    /**
     * Spring-specific LocalizationContext adapter that merges session-scoped
     * JSTL LocalizationContext/Locale attributes with the local Spring request context.
     */
    private static class SpringLocalizationContext extends LocalizationContext {

        private final MessageSource messageSource;

        private final HttpServletRequest request;

        public SpringLocalizationContext(MessageSource messageSource, HttpServletRequest request) {
            this.messageSource = messageSource;
            this.request = request;
        }

        @Override
        public ResourceBundle getResourceBundle() {
            HttpSession session = this.request.getSession(false);
            if (session != null) {
                Object lcObject = Config.get(session, Config.FMT_LOCALIZATION_CONTEXT);
                if (lcObject instanceof LocalizationContext) {
                    ResourceBundle lcBundle = ((LocalizationContext) lcObject).getResourceBundle();
                    return new MessageSourceResourceBundle(this.messageSource, getLocale(), lcBundle);
                }
            }
            return new MessageSourceResourceBundle(this.messageSource, getLocale());
        }

        @Override
        public Locale getLocale() {
            HttpSession session = this.request.getSession(false);
            if (session != null) {
                Object localeObject = Config.get(session, Config.FMT_LOCALE);
                if (localeObject instanceof Locale) {
                    return (Locale) localeObject;
                }
            }
            return RequestContextUtils.getLocale(this.request);
        }
    }

}
